Did you try to return false from this.bar? I wonder if this would stop the other controller from processing the event... Is this even what you are trying to accomplish? I know you can stop an application event if you return false.

That won't resolve my problem because my controllers are loaded dynamically by demand, so whichever comes first should register the event and avoid duplication from other controllers that can also be loaded.

Normally extJS eventBus supports duplication of events. They are organized something like this:

example:

click:
controller1 #mygrid
controller2 #mygrid

What I would like to do is to tell eventBus not to register an event if the itemId already exists under the same handler (click).